This invention relates to a device for the withdrawal of fluids from patient cavities. More specifically, the present invention comprises a device that can be utilized adjacent to or directly upon a catheter used for the withdrawal of such fluids and which operates at predetermined intervals to return, under a positive pressure, a minute quantity of that withdrawn fluid back into the catheter to clear the withdrawal passageways.
Intermittent suction devices are used regularly to remove fluids from patients cavities, such as the stomach, and typically are utilized post-operatively. Such devices can operate from a main source of vacuum that is available in hospital recovery rooms by means of central piping systems.
In non-intermittent suction units, the hospital vacuum system withdraws the fluids continuously into some receiver and discontinues the withdrawing cycle only when the collection container is full or hospital personnel disconnect the system.
With intermittent suction, the continuous withdrawing of fluids is intermittently discontinued at timed intervals. In some units, the vacuum applied by the tubing withdrawing the fluids is cycled to atmospheric pressure so that the portion of the fluid moves backwardly toward the patient in order to clear obstructions in the line or to move the catheter away from the wall of the stomach. One difficulty with such systems is that the back flush is carried out to some extent by gravitational forces and therefore the collection container needed to be located at an elevation higher than the patient. Often such devices are incorporated into the timing apparatus itself on the hospital wall at the height of the receptacle providing the vacuum. In addition, gravity force often was not effective in that the tubing carrying fluid from the patient seldom contained a solid line of liquid but more often carried pockets of gas. A typical device of the type that returned the line withdrawing fluids to atmospheric pressure is shown and described in U.S. Pat. No. 3,659,605 of Ulrich Sielaff.
In an effort to correct some of the problems, positive pulse devices have been proposed and which send a positive quantity of fluid backwards toward the patient to flush the passageways. One of such devices is shown and described in U.S. Pat. No. 4,315,506 to Kayser, et al.
One of the difficulties with the Kayser, et al. device is, however, that it features an expandable reflux chamber actually in the suction line to the patient. That reflux chamber comprises a piston that is withdrawn to expand the reflux chamber and, at the predetermined time interval, the piston moves to collapse the reflux chamber, forcing the contents therein back towards the patient to clear the passageways of obstructions.
By use of a single piston and expandable chamber, however, most of the stroke of the Kayser, et al. piston occurs with the patient line open but the line from the vacuum source closed. Thus, the expanding reflux chamber actually draws a further vacuum on the patient cavity being drained. It is therefore possible to increase the amount of vacuum applied to the patient to an amount in excess of the regulated vacuum established by a doctor as suitable for that patient.
The possibility of the Kayser, et al. device itself actually drawing an excessive vacuum on the patient prevented application of the Kayser, et al. device at or on the catheter to the patient. Such catheters are relatively inflexible and thus the drawing of such vacuum at or near the actual catheter opening would have the most severe effect on that vacuum reaching the patient cavity. Thus, the practical location of the Kayser, et al. device was contemplated to be at the end of the tubing connecting the catheter to other equipment such as the collection bottle. Generally, that tubing was in the order of six (6) feet in length and for convenience, typical tubing for withdrawing fluids is relatively flexible and thus also distensible.
Accordingly, the use of the Kayser, et al. device remote from the actual patient catheter created a reservoir effect in the flexible tubing. The amount of fluid returned to the patient line to clear obstructions therefore had to be relatively large since its effect was dissipated in the reservoir created by the long length of distensible tubing and it was necessary that the returned volume have an effect at the end of the catheter within the patient to clear that catheter from becoming attached to inner walls of the cavity being drained.
Thus the Kayser, et al. device required a relatively large volume, structure and could only be used remote from the patient catheter.